1. Field of the Invention
The present invention relates to a dynamic frequency selection (DFS) mechanism in an IEEE 802.11(h) wireless local area network (WLAN), wherein the operational channel of the WLAN is selected dynamically according to channel determination made by the access point (AP) based on a channel quality report.
2. Description of the Invention
The medium access control (MAC) and physical characteristics for wireless local area networks (WLANs) to support physical layer units are specified in IEEE 802.11 standard, which is defined in International Standard ISO/IEC 8802-11,“Information Technology—Telecommunications and information exchange area networks”, 1999 Edition, which is hereby incorporated by reference in its entirety. The standard specifies two variants WLAN: infrastructure-based and ad-hoc type. In the former network, communication typically takes place only between the wireless nodes, called stations (STAs) and the access point (AP), not directly between the wireless nodes as in the latter network. The STAs and the AP, which are within the same radio coverage, are known as a basic service set (BSS).
When two adjacent basic service sets (BSSs) are located close to each other and operate at the same channel, which are referred to as overlapping BSSs, it is difficult to support the required quality-of-service (Qos) due to the possible mutual interference between the overlapping BSSs. In addition, other co-located systems (for example, HIPERLAN/2 device as set forth in the European Radio communications Committee (ERC) regulatory) near a particular STA, may cause reception interference. It is not always possible to avoid interference by carefully planning channel allocations to BSSs before the WLAN deployment, especially in the home/office environment where other WLAN devices are operating independently in the vicinity, for example, in the neighboring houses or offices.
Accordingly, there is a need for a dynamic frequency selection (DFS) scheme that can be incorporated into IEEE 802.11 standard, enabling the access point (AP) to select a channel for all stations (STAs) associated with its basic service set (BSS). To achieve this, the present invention introduces changes to the 802.11 Medium Access Control (MAC) and 802.11a Physical Layer (PHY) (for IEEE 802.11 WLAN operation at the 5 GHz unlicensed bands) specifications, which would allow dynamic selection of a frequency channel for the operation of the network. This would facilitate meeting the requirements imposed by the European Radio communications Committee (ERC) and it would enhance the performance of an 802.11 WLAN operation in the 5 GHz band.